Study of the structure and deviation from equilibrium in direct current supersonic plasma jets

Selezneva, S. E.; Rajabian, Mahmoud; Gravelle, Denis; Boulos, Maher I.

doi:10.1088/0022-3727/34/18/321

Cited by 28 publications

(51 citation statements)

References 26 publications

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“…This may result in the strong drop of the heavy particle temperature in the expansion region with respect to the temperature of free electrons. On the other hand, in the shock region, the heavy particle temperature may even exceed the electron temperature [31,32]. From the present results and from the assumption that the populations of excited species can be in partial equilibrium with free electrons, we suppose the temperature we have obtained may be close to the temperature of free electrons.…”

Section: Resultssupporting

confidence: 55%

Spectroscopic Characterization of a Steam Arc Cutting Torch

Sember

Mašláni

Křenek

et al. 2011

Plasma Chem Plasma Process

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Optical emission spectroscopy has been used to investigate the characteristics of a plasma jet produced by a steam arc cutting torch operated in air at atmospheric pressure. A procedure has been developed for simultaneous determination of temperature and pressure in the plasma jet as well as an effective nonequilibrium factor. It is based on comparison of a few experimental and simulated spectral quantities. The experimental data were obtained from the spectrum of H b and OII lines centred at 480 nm. The existence of the shock wave structure characteristic of an underexpanded jet can clearly be deduced from the measured properties. In the first expansion region, the centreline pressure drops from about 1.4 atm at the nozzle exit to about 0.7 atm a few tenths of millimeter downstream. On the contrary, the centreline temperature remains almost unchanged within this region and reaches the value of about 23,000 K.

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Section: Resultssupporting

confidence: 55%

Spectroscopic Characterization of a Steam Arc Cutting Torch

Sember

Mašláni

Křenek

et al. 2011

Plasma Chem Plasma Process

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“…The RNG k-ε model has been proved to provide accurate and reliable results for a wide class of flows with high Reynolds number and pressure gradient, particularly for internal nozzle flows [4,[6][7][8][9]. In addition, Zhu et al [10] showed that the RNG k-ε model provided flow fields for the system configuration and Mach number similar to those of this study, in better agreement with experiments than any other turbulence model.…”

Section: Governing Equationssupporting

confidence: 75%

Effect of Unsteadiness and Nozzle Asymmetry on Thrust of a Microthruster

Kim

Kwon

Lee

2012

Nanoscale and Microscale Thermophysical Engineering

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Due to the small size and short propulsion pulses of solid propellant microthrusters, unsteady characteristics and/or fabrication errors may cause appreciable effects on the total thrust. The present work simulates a 2D planar and conical nozzle of 200 µm throat diameter using the traditional momentum equations and turbulence closure model. Unsteady characteristics were found to be insensitive to the inlet mass flux but sensitive to the chamber size. The characteristic time of transient momentum variations in the nozzle was found to be on the order of 0.1 ms, and that for decay was smaller than that for development by about 25%. This work confirmed that the magnitude of thrust was not sensitive to distortions in the nozzle geometry. A mismatch of the nozzle throat changed the position of sonic plane, but its effect on thrust was almost negligible.

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“…In the plasma jet, the plasma is formed and accelerated at the same time and the collision process cannot establish thermal and ionization equilibrium [39]. Our work proves that excitation equilibrium cannot establish, either.…”

Section: Resultsmentioning

confidence: 64%

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

Wang

et al. 2015

Appl. Phys. B

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radical-based chemistry generally dominates in any eventual material processing in the plasma jet.The CH radical is a common intermediate in reactive chemical systems with hydrocarbons [6]. Monitoring CH provides an insight into the reaction mechanism. CH radicals and C atoms contribute to the experimentally observed high and nonuniform diamond growth rates in the highpower Bristol reactor [7]. The level of CH concentration agreement between the model prediction and the experimental measurement can be used to test model predictions of hydrocarbon chemistry [8]. CH also is a probe species to determine the chemical erosion of carbon-based materials in divertor [9].Optical emission spectroscopy (OES) is arguably the simplest and most straightforward means to investigate the CH behavior in the plasma. The OES signal is proportional to the population density of the upper state, and the interpretation of OES data is complicated which needs a proper understanding of the various species excitation and de-excitation processes, especially when the plasma does not close to local thermodynamic equilibrium (LTE). Generally, the ground electronic state radicals and molecules are inevitably present in higher concentrations than their electronically excited counterparts and dominate the thin film deposition [10]. Thus, it is necessary to measure the majority species populating ground and low-lying electronic states.To diagnose the ground state, absorption spectroscopy is a preferred approach. Cavity ring-down spectroscopy (CRDS) [11] provides the diagnostic of choice to obtain the absolute number densities without the need for additional calibration standards. The technique measures the time decay of a laser pulse trapped in a high-finesse optical cavity. Effectively, it is a multi-pass technique in which the optical path length may be tens of kilometers. Thus, it is a versatile, highly sensitive, linear absorption technique.Abstract A combination of optical emission spectroscopy (OES) and cavity ring-down spectroscopy (CRDS) has enabled to determinate the number densities of CH(A 2 Δ) and CH(X 2 Π) radicals simultaneously in a cascaded arc plasma reactor operating with a CH 4 /Ar mixture. It is found that the number density of CH(A 2 Δ) radical increases with discharge current at first and then decreases. However, the number density of CH(X 2 Π) radical decreases with discharge current when the rate of CH 4 flow to total flow is lower than 1 %, while it increases slightly with discharge current when the rate is 1.5 %. The results reveal that CH radicals are deviation from excitation equilibrium. Although OES is the simplest and most straightforward means to investigate the CH radical behavior, it is not enough to provide the information of the CH(X 2 Π) number density, and additional methods, such as CRDS, are needed in the cascaded arc plasma jet.

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Study of the structure and deviation from equilibrium in direct current supersonic plasma jets

Cited by 28 publications

References 26 publications

Spectroscopic Characterization of a Steam Arc Cutting Torch

Spectroscopic Characterization of a Steam Arc Cutting Torch

Effect of Unsteadiness and Nozzle Asymmetry on Thrust of a Microthruster

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

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